1. Field of the Invention
The present invention relates to a control apparatus for a vehicle, particularly a control apparatus for a vehicle calculating target acceleration to have the driving force controlled based on the calculated target acceleration.
2. Description of the Background Art
It is conventionally known that the acceleration of a vehicle greatly affects the drivability. In other words, the driver will sense discomfort if the acceleration is too great or too small. It is therefore necessary to appropriately control the acceleration of a vehicle.
Japanese Patent Laying-Open No. 10-009018 discloses a driving force control device for a vehicle that can provide an appropriate feel of acceleration. The driving force control device disclosed in this publication controls the driving force of a vehicle in which the vibration in the longitudinal direction is reduced by temporarily decreasing the engine output at the time of resuming fuel supply from a coasting state in which fuel supply is ceased. This driving force control device includes a detection unit detecting the accelerator press-down degree, a throttle control unit that can control the throttle opening of the engine independent of the accelerator press-down degree, and a driving force rate change limiter limiting the changing rate of the target driving force with respect to change in the accelerator when output control is executed through vibration reducer.
In accordance with the driving force control device disclosed in the publication set forth above, the engine output property is corrected so as to suppress torsional vibration of the driveline at the time of reacceleration from a coasting state. At the same time, the changing property of the target driving force is limited with respect to the change in the accelerator. When the changing rate or changing amount of the accelerator is greater than a predetermined value, the target driving force is limited, whereby the acceleration property becomes more gentle than the actual change in the accelerator. Accordingly, vibration in the longitudinal direction of the vehicle at the time of reacceleration is suppressed to provide a better feel of acceleration. The abrupt feel of acceleration that becomes excessive can be suppressed effectively by rendering gentle the actual acceleration property with respect to change in the accelerator.
The driving force control device disclosed in Japanese Patent Laying-Open No. 10-009018 is disadvantageous in that the acceleration property may not be rendered gentle in the region where the changing property of the target driving force is not limited, leading to the possibility of applying discomfort to the occupant caused by the abrupt acceleration. Further, if the changing rate of the target driving force is limited, the target driving force per se will be also limited correspondingly. The expected feel of acceleration cannot be obtained in the case where the occupant wishes for prompt acceleration. There was a problem of applying discomfort to the occupant of the vehicle.